Egypt has tightened rules for issuing entry visas to tourists due to security concerns, according to security sources, in a move which tourism officials fear could further damaged their industry.The Egyptian cabinet said late on Thursday it had decided to cancel the option of obtaining a tourist visa at Egyptian airports to individuals or groups travelling independently. It said only groups travelling through licensed tour operators would be granted entry visas at Egyptian airports. Others must obtain visas in their home countries before travelling. \"This is a security measure and we have asked for it,\" one security source said. He could not say if senior officials had requested the step as a precautionary measure or were prompted by \"cases of foreigners trying to enter Egypt to conduct illegal actions\". Egypt in July detained four US nationals for taking pictures in the Suez Canal area and an Italian for taking pictures of a military building in Cairo.The chairman of Egypt\'s Tourism Authority, Amr El-Ezaby, told state news agency MENA on Friday the decision would \"harm the flow of tourism to Egypt ... and is not understood and its purpose is also not understood\". Tourism, a main pillar of the Egyptian economy, was hit hard after the uprising that toppled President Hosni Mubarak in February but has been recovering slowly since then. On Thursday, the Egyptian Ministry of Planning said in a statement that tourism revenues in 2010-11 were $10.6 billion down from $11.6 billion in 2009-10. The decision caused confusion among passengers at Cairo\'s International airport on Friday, airport sources said.\"The government should have consulted with tourism and airline experts before issuing such a decision ... as tourism and airline companies depend on the ease of issuing entry visas,\" one airport source said.